<?php  // $Id: report.php,v 1.41.2.8 2008/11/27 04:48:11 tjhunt Exp $

	require_once($CFG->libdir.'/tablelib.php');

/// Item analysis displays a table of quiz questions and their performance
class quiz_report extends quiz_default_report {

	function display($quiz, $cm, $course) {	 /// This function just displays the report
		global $CFG, $SESSION, $QTYPES;
		$strnoattempts = get_string('noattempts','quiz');
	/// Only print headers if not asked to download data
		$download = optional_param('download', NULL);
		if (!$download) {
			$this->print_header_and_tabs($cm, $course, $quiz, $reportmode="analysis");
		}
	/// Construct the table for this particular report

		if (!$quiz->questions) {
			print_heading($strnoattempts);
			return true;
		}

	/// Check to see if groups are being used in this quiz
		$currentgroup = groups_get_activity_group($cm, true);
		
		if ($groupmode = groups_get_activity_groupmode($cm)) {   // Groups are being used
			if (!$download) {
				groups_print_activity_menu($cm, "report.php?id=$cm->id&amp;mode=analysis");
			}
		}

		// set Table and Analysis stats options
		if(!isset($SESSION->quiz_analysis_table)) {
			$SESSION->quiz_analysis_table = array('attemptselection' => 0, 'lowmarklimit' => 0, 'pagesize' => QUIZ_REPORT_DEFAULT_PAGE_SIZE);
		}

		foreach($SESSION->quiz_analysis_table as $option => $value) {
			$urlparam = optional_param($option, NULL, PARAM_INT);
			if($urlparam === NULL) {
				$$option = $value;
			} else {
				$$option = $SESSION->quiz_analysis_table[$option] = $urlparam;
			}
		}
		if (!isset($pagesize) || ((int)$pagesize < 1) ){
			$pagesize = QUIZ_REPORT_DEFAULT_PAGE_SIZE;
		}


		$scorelimit = $quiz->sumgrades * $lowmarklimit/ 100;

		// ULPGC ecastro DEBUG this is here to allow for different SQL to select attempts
		switch ($attemptselection) {
		case QUIZ_ALLATTEMPTS :
			$limit = '';
			$group = '';
			break;
		case QUIZ_HIGHESTATTEMPT :
			$limit = ', max(qa.sumgrades) ';
			$group = ' GROUP BY qa.userid ';
			break;
		case QUIZ_FIRSTATTEMPT :
			$limit = ', min(qa.timemodified) ';
			$group = ' GROUP BY qa.userid ';
			break;
		case QUIZ_LASTATTEMPT :
			$limit = ', max(qa.timemodified) ';
			$group = ' GROUP BY qa.userid ';
			break;
		}

		if ($attemptselection != QUIZ_ALLATTEMPTS) {
			$sql = 'SELECT qa.userid '.$limit.
					'FROM '.$CFG->prefix.'user u LEFT JOIN '.$CFG->prefix.'quiz_attempts qa ON u.id = qa.userid '.
					'WHERE qa.quiz = '.$quiz->id.' AND qa.preview = 0 '.
					$group;
			$usermax = get_records_sql_menu($sql);
		}

		$groupmembers = '';
		$groupwhere = '';

		//Add this to the SQL to show only group users
		if ($currentgroup) {
			$groupmembers = ", {$CFG->prefix}groups_members gm ";
			$groupwhere = "AND gm.groupid = '$currentgroup' AND u.id = gm.userid";
		}

		$sql = 'SELECT  qa.* FROM '.$CFG->prefix.'quiz_attempts qa, '.$CFG->prefix.'user u '.$groupmembers.
				 'WHERE u.id = qa.userid AND qa.quiz = '.$quiz->id.' AND qa.preview = 0 AND ( qa.sumgrades >= '.$scorelimit.' ) '.$groupwhere;

		// ^^^^^^ es posible seleccionar aqu TODOS los quizzes, como quiere Jussi,
		// pero haba que llevar la cuenta ed cada quiz para restaura las preguntas (quizquestions, states)

		/// Fetch the attempts
		$attempts = get_records_sql($sql);

		if(empty($attempts)) {
			print_heading(get_string('nothingtodisplay'));
			$this->print_options_form($quiz, $cm, $attemptselection, $lowmarklimit, $pagesize);
			return true;
		}

	/// Here we rewiew all attempts and record data to construct the table
		$questions = array();
		$statstable = array();
		$questionarray = array();
		foreach ($attempts as $attempt) {
			$questionarray[] = quiz_questions_in_quiz($attempt->layout);
		}
		$questionlist = quiz_questions_in_quiz(implode(",", $questionarray));
		$questionarray = array_unique(explode(",",$questionlist));
		$questionlist = implode(",", $questionarray);
		unset($questionarray);

		foreach ($attempts as $attempt) {
			switch ($attemptselection) {
			case QUIZ_ALLATTEMPTS :
				$userscore = 0;	  // can be anything, not used
				break;
			case QUIZ_HIGHESTATTEMPT :
				$userscore = $attempt->sumgrades;
				break;
			case QUIZ_FIRSTATTEMPT :
				$userscore = $attempt->timemodified;
				break;
			case QUIZ_LASTATTEMPT :
				$userscore = $attempt->timemodified;
				break;
			}

			if ($attemptselection == QUIZ_ALLATTEMPTS || $userscore == $usermax[$attempt->userid]) {

			$sql = "SELECT q.*, i.grade AS maxgrade, i.id AS instance".
				   "  FROM {$CFG->prefix}question q,".
				   "	   {$CFG->prefix}quiz_question_instances i".
				   " WHERE i.quiz = '$quiz->id' AND q.id = i.question".
				   "   AND q.id IN ($questionlist)";

			if (!$quizquestions = get_records_sql($sql)) {
				error('No questions found');
			}

			// Load the question type specific information
			if (!get_question_options($quizquestions)) {
				error('Could not load question options');
			}
			// Restore the question sessions to their most recent states
			// creating new sessions where required
			if (!$states = get_question_states($quizquestions, $quiz, $attempt)) {
				error('Could not restore question sessions');
			}
			$numbers = explode(',', $questionlist);
			$statsrow = array();
			foreach ($numbers as $i) {
				if (!isset($quizquestions[$i]) or !isset($states[$i])) {
					continue;
				}
				$qtype = ($quizquestions[$i]->qtype=='random') ? $states[$i]->options->question->qtype : $quizquestions[$i]->qtype;
				$q = get_question_responses($quizquestions[$i], $states[$i]);
				if (empty($q)){
					continue;
				}
				$qid = $q->id;
				if (!isset($questions[$qid])) {
					$questions[$qid]['id'] = $qid;
					$questions[$qid]['qname'] = $quizquestions[$i]->name;
					foreach ($q->responses as $answer => $r) {
						$r->count = 0;
						$questions[$qid]['responses'][$answer] = $r->answer;
						$questions[$qid]['rcounts'][$answer] = 0;
						$questions[$qid]['credits'][$answer] = $r->credit;
						$statsrow[$qid] = 0;
					}
				}
				$responses = get_question_actual_response($quizquestions[$i], $states[$i]);
				foreach ($responses as $resp){
					if ($resp) {
						if ($key = array_search($resp, $questions[$qid]['responses'])) {
							$questions[$qid]['rcounts'][$key]++;
						} else {
							$test = new stdClass;
							$test->responses = $QTYPES[$quizquestions[$i]->qtype]->get_correct_responses($quizquestions[$i], $states[$i]);
							if ($key = $QTYPES[$quizquestions[$i]->qtype]->check_response($quizquestions[$i], $states[$i], $test)) {
								$questions[$qid]['rcounts'][$key]++;
							} else {
								$questions[$qid]['responses'][] = $resp;
								$questions[$qid]['rcounts'][] = 1;
								$questions[$qid]['credits'][] = 0;
							}
						}
					}
				}
				$statsrow[$qid] = get_question_fraction_grade($quizquestions[$i], $states[$i]);
			}
			$attemptscores[$attempt->id] = $attempt->sumgrades;
			$statstable[$attempt->id] = $statsrow;
			}
		} // Statistics Data table built

		unset($attempts);
		unset($quizquestions);
		unset($states);

		// now calculate statistics and set the values in the $questions array
		$top = max($attemptscores);
		$bottom = min($attemptscores);
		$gap = ($top - $bottom)/3;
		$top -=$gap;
		$bottom +=$gap;
		foreach ($questions as $qid=>$q) {
			$questions[$qid] = $this->report_question_stats($q, $attemptscores, $statstable, $top, $bottom);
		}
		unset($attemptscores);
		unset($statstable);

	/// Now check if asked download of data
		if ($download = optional_param('download', NULL)) {
			$filename = clean_filename("$course->shortname ".format_string($quiz->name,true));
			switch ($download) {
			case "Excel" :
				$this->Export_Excel($questions, $filename);
				break;
			case "ODS":
				$this->Export_ODS($questions, $filename);
				break;
			case "CSV":
				$this->Export_CSV($questions, $filename);
				break;
			}
		}

	/// Construct the table for this particular report

		$tablecolumns = array('id', 'qname',	'responses', 'credits', 'rcounts', 'rpercent', 'facility', 'qsd','disc_index', 'disc_coeff');
		$tableheaders = array(get_string('qidtitle','quiz_analysis'), get_string('qtexttitle','quiz_analysis'),
						get_string('responsestitle','quiz_analysis'), get_string('rfractiontitle','quiz_analysis'),
						get_string('rcounttitle','quiz_analysis'), get_string('rpercenttitle','quiz_analysis'),
						get_string('facilitytitle','quiz_analysis'), get_string('stddevtitle','quiz_analysis'),
						get_string('dicsindextitle','quiz_analysis'), get_string('disccoefftitle','quiz_analysis'));

		$table = new flexible_table('mod-quiz-report-itemanalysis');

		$table->define_columns($tablecolumns);
		$table->define_headers($tableheaders);
		$table->define_baseurl($CFG->wwwroot.'/mod/quiz/report.php?q='.$quiz->id.'&amp;mode=analysis');

		$table->sortable(true);
		$table->no_sorting('rpercent');
		$table->collapsible(true);
		$table->initialbars(false);

		$table->column_class('id', 'numcol');
		$table->column_class('credits', 'numcol');
		$table->column_class('rcounts', 'numcol');
		$table->column_class('rpercent', 'numcol');
		$table->column_class('facility', 'numcol');
		$table->column_class('qsd', 'numcol');
		$table->column_class('disc_index', 'numcol');
		$table->column_class('disc_coeff', 'numcol');

		$table->column_suppress('id');
		$table->column_suppress('qname');
		$table->column_suppress('facility');
		$table->column_suppress('qsd');
		$table->column_suppress('disc_index');
		$table->column_suppress('disc_coeff');

		$table->set_attribute('cellspacing', '0');
		$table->set_attribute('id', 'itemanalysis');
		$table->set_attribute('class', 'generaltable generalbox');

		// Start working -- this is necessary as soon as the niceties are over
		$table->setup();

		$tablesort = $table->get_sql_sort();
		$sorts = explode(",",trim($tablesort));
		if ($tablesort and is_array($sorts)) {
			$sortindex = array();
			$sortorder = array ();
			foreach ($sorts as $sort) {
				$data = explode(" ",trim($sort));
				$sortindex[] = trim($data[0]);
				$s = trim($data[1]);
				if ($s=="ASC") {
					$sortorder[] = SORT_ASC;
				} else {
					$sortorder[] = SORT_DESC;
				}
			}
			if (count($sortindex)>0) {
				$sortindex[] = "id";
				$sortorder[] = SORT_ASC;
				foreach($questions as $qid => $row){
					$index1[$qid] = $row[$sortindex[0]];
					$index2[$qid] = $row[$sortindex[1]];
				}
				array_multisort($index1, $sortorder[0], $index2, $sortorder[1], $questions);
			}
		}

		$format_options = new stdClass;
		$format_options->para = false;
		$format_options->noclean = true;
		$format_options->newlines = false;

		// Now it is time to page the data, simply slice the keys in the array
		$table->pagesize($pagesize, count($questions));
		$start = $table->get_page_start();
		$pagequestions = array_slice(array_keys($questions), $start, $pagesize);

		foreach($pagequestions as $qnum) {
			$q = $questions[$qnum];
			$qid = $q['id'];
			$question = get_record('question', 'id', $qid);
			if (question_has_capability_on($question, 'edit') || question_has_capability_on($question, 'view')) {
				$qnumber = " (".link_to_popup_window('/question/question.php?id='.$qid.'&amp;cmid='.$cm->id, 'editquestion', $qid, 450, 550, get_string('edit'), 'none', true ).") ";
			} else {
				$qnumber = $qid;
			}
			$qname = '<div class="qname">'.format_text($question->name." :  ", $question->questiontextformat, $format_options, $quiz->course).'</div>';
			$qicon = print_question_icon($question, true);
			$qreview = quiz_question_preview_button($quiz, $question);
			$qtext = format_text($question->questiontext, $question->questiontextformat, $format_options, $quiz->course);
			$qquestion = $qname."\n".$qtext."\n";

			$responses = array();
			foreach ($q['responses'] as $aid=>$resp){
				$response = new stdClass;
				if ($q['credits'][$aid] <= 0) {
					$qclass = 'uncorrect';
				} elseif ($q['credits'][$aid] == 1) {
					$qclass = 'correct';
				} else {
					$qclass = 'partialcorrect';
				}
				$response->credit = '<span class="'.$qclass.'">('.format_float($q['credits'][$aid],2).') </span>';
				$response->text = '<span class="'.$qclass.'">'.format_text($resp, FORMAT_MOODLE, $format_options, $quiz->course).' </span>';
				$count = $q['rcounts'][$aid].'/'.$q['count'];
				$response->rcount = $count;
				$response->rpercent =  '('.format_float($q['rcounts'][$aid]/$q['count']*100,0).'%)';
				$responses[] = $response;
			}

			$facility = format_float($q['facility']*100,0)."%";
			$qsd = format_float($q['qsd'],3);
			$di = format_float($q['disc_index'],2);
			$dc = format_float($q['disc_coeff'],2);

			$response = array_shift($responses);
			$table->add_data(array($qnumber."\n<br />".$qicon."\n ".$qreview, $qquestion, $response->text, $response->credit, $response->rcount, $response->rpercent, $facility, $qsd, $di, $dc));
			foreach($responses as $response) {
				$table->add_data(array('', '', $response->text, $response->credit, $response->rcount, $response->rpercent, '', '', '', ''));
			}
		}

		print_heading_with_help(get_string("analysistitle", "quiz_analysis"),"itemanalysis", "quiz");

		echo '<div id="tablecontainer">';
		$table->print_html();
		echo '</div>';

		$this->print_options_form($quiz, $cm, $attemptselection, $lowmarklimit, $pagesize);
		return true;
	}


	function print_options_form($quiz, $cm, $attempts, $lowlimit=0, $pagesize=QUIZ_REPORT_DEFAULT_PAGE_SIZE) {
		global $CFG, $USER;
		echo '<div class="controls">';
		echo '<form id="options" action="report.php" method="post">';
		echo '<fieldset class="invisiblefieldset">';
		echo '<p class="quiz-report-options">'.get_string('analysisoptions', 'quiz').': </p>';
		echo '<input type="hidden" name="id" value="'.$cm->id.'" />';
		echo '<input type="hidden" name="q" value="'.$quiz->id.'" />';
		echo '<input type="hidden" name="mode" value="analysis" />';
		echo '<p><label for="menuattemptselection">'.get_string('attemptselection', 'quiz_analysis').'</label> ';
		$options = array ( QUIZ_ALLATTEMPTS	 => get_string("attemptsall", 'quiz_analysis'),
						   QUIZ_HIGHESTATTEMPT => get_string("attemptshighest", 'quiz_analysis'),
						   QUIZ_FIRSTATTEMPT => get_string("attemptsfirst", 'quiz_analysis'),
						   QUIZ_LASTATTEMPT  => get_string("attemptslast", 'quiz_analysis'));
		choose_from_menu($options, "attemptselection", "$attempts", "");
		echo '</p>';
		echo '<p><label for="lowmarklimit">'.get_string('lowmarkslimit', 'quiz_analysis').'</label> ';
		echo '<input type="text" id="lowmarklimit" name="lowmarklimit" size="1" value="'.$lowlimit.'" /> % </p>';
		echo '<p><label for="pagesize">'.get_string('pagesize', 'quiz_analysis').'</label> ';
		echo '<input type="text" id="pagesize" name="pagesize" size="1" value="'.$pagesize.'" /></p>';
		echo '<p><input type="submit" value="'.get_string('go').'" />';
		helpbutton("analysisoptions", get_string("analysisoptions",'quiz_analysis'), 'quiz');
		echo '</p>';
		echo '</fieldset>';
		echo '</form>';
		echo '</div>';
		echo "\n";

		echo '<table class="boxaligncenter"><tr>';
		$options = array();
		$options["id"] = "$cm->id";
		$options["q"] = "$quiz->id";
		$options["mode"] = "analysis";
		$options['sesskey'] = $USER->sesskey;
		$options["noheader"] = "yes";
		echo '<td>';
		$options["download"] = "ODS";
		print_single_button("report.php", $options, get_string("downloadods"));
		echo "</td>\n";
		echo '<td>';
		$options["download"] = "Excel";
		print_single_button("report.php", $options, get_string("downloadexcel"));
		echo "</td>\n";

		if (file_exists("$CFG->libdir/phpdocwriter/lib/include.php")) {
			echo '<td>';
			$options["download"] = "OOo";
			print_single_button("report.php", $options, get_string("downloadooo", "quiz_analysis"));
			echo "</td>\n";
		}
		echo '<td>';
		$options["download"] = "CSV";
		print_single_button('report.php', $options, get_string("downloadtext"));
		echo "</td>\n";
		echo "<td>";
		helpbutton('analysisdownload', get_string('analysisdownload', 'quiz_analysis'), 'quiz');
		echo "</td>\n";
		echo '</tr></table>';
}

	function report_question_stats(&$q, &$attemptscores, &$questionscores, $top, $bottom) {
		$qstats = array();
		$qid = $q['id'];
		$top_scores = $top_count = 0;
		$bottom_scores = $bottom_count = 0;
		foreach ($questionscores as $aid => $qrow){
			if (isset($qrow[$qid])){
				$qstats[] =  array($attemptscores[$aid],$qrow[$qid]);
				if ($attemptscores[$aid]>=$top){
					$top_scores +=$qrow[$qid];
					$top_count++;
				}
				if ($attemptscores[$aid]<=$bottom){
					$bottom_scores +=$qrow[$qid];
					$bottom_count++;
				}
			}
		}
		$n = count($qstats);
		$sumx = stats_sumx($qstats, array(0,0));
		$sumg = $sumx[0];
		$sumq = $sumx[1];
		$sumx2 = stats_sumx2($qstats, array(0,0));
		$sumg2 = $sumx2[0];
		$sumq2 = $sumx2[1];
		$sumxy = stats_sumxy($qstats, array(0,0));
		$sumgq = $sumxy[0];

		$q['count'] = $n;
		$q['facility'] = $sumq/$n;
		if ($n<2) {
			$q['qsd'] = sqrt(($sumq2 - $sumq*$sumq/$n)/($n));
			$gsd = sqrt(($sumg2 - $sumg*$sumg/$n)/($n));
		} else {
			$q['qsd'] = sqrt(($sumq2 - $sumq*$sumq/$n)/($n-1));
			$gsd = sqrt(($sumg2 - $sumg*$sumg/$n)/($n-1));
		}
		$q['disc_index'] = ($top_scores - $bottom_scores)/max($top_count, $bottom_count, 1);
		$div = $n*$gsd*$q['qsd'];
		if ($div!=0) {
			$q['disc_coeff'] = ($sumgq - $sumg*$sumq/$n)/$div;
		} else {
			$q['disc_coeff'] = -999;
		}
		return $q;
	}

	function Export_Excel(&$questions, $filename) {
		global $CFG;
		require_once("$CFG->libdir/excellib.class.php");

	/// Calculate file name
		$filename .= ".xls";
	/// Creating a workbook
		$workbook = new MoodleExcelWorkbook("-");
	/// Sending HTTP headers
		$workbook->send($filename);
	/// Creating the first worksheet
		$sheettitle = get_string('reportanalysis','quiz_analysis');
		$myxls =& $workbook->add_worksheet($sheettitle);
	/// format types
		$format =& $workbook->add_format();
		$format->set_bold(0);
		$formatbc =& $workbook->add_format();
		$formatbc->set_bold(1);
		$formatb =& $workbook->add_format();
		$formatb->set_bold(1);
		$formaty =& $workbook->add_format();
		$formaty->set_bg_color('yellow');
		$formatyc =& $workbook->add_format();
		$formatyc->set_bg_color('yellow'); //bold text on yellow bg
		$formatyc->set_bold(1);
		$formatyc->set_align('center');
		$formatc =& $workbook->add_format();
		$formatc->set_align('center');
		$formatbc->set_align('center');
		$formatbpct =& $workbook->add_format();
		$formatbpct->set_bold(1);
		$formatbpct->set_num_format('0.0%');
		$formatbrt =& $workbook->add_format();
		$formatbrt->set_bold(1);
		$formatbrt->set_align('right');
		$formatred =& $workbook->add_format();
		$formatred->set_bold(1);
		$formatred->set_color('red');
		$formatred->set_align('center');
		$formatblue =& $workbook->add_format();
		$formatblue->set_bold(1);
		$formatblue->set_color('blue');
		$formatblue->set_align('center');
	/// Here starts workshhet headers
		$myxls->write_string(0,0,$sheettitle,$formatb);

		$headers = array(get_string('qidtitle','quiz_analysis'), get_string('qtypetitle','quiz_analysis'),
						get_string('qnametitle','quiz_analysis'), get_string('qtexttitle','quiz_analysis'),
						get_string('responsestitle','quiz_analysis'), get_string('rfractiontitle','quiz_analysis'),
						get_string('rcounttitle','quiz_analysis'), get_string('rpercenttitle','quiz_analysis'),
						get_string('qcounttitle','quiz_analysis'),
						get_string('facilitytitle','quiz_analysis'), get_string('stddevtitle','quiz_analysis'),
						get_string('dicsindextitle','quiz_analysis'), get_string('disccoefftitle','quiz_analysis'));

		foreach ($headers as $key => $header) {
			$headers[$key] = preg_replace('/<br[^>]*>/', ' ', $header);
		}

		$col = 0;
		foreach ($headers as $item) {
			$myxls->write(2,$col,$item,$formatbc);
			$col++;
		}

		$row = 3;
		foreach($questions as $q) {
			$rows = $this->print_row_stats_data($q);
			foreach($rows as $rowdata){
				$col = 0;
				foreach($rowdata as $item){
					$myxls->write($row,$col,$item,$format);
					$col++;
				}
				$row++;
			}
		}
	/// Close the workbook
		$workbook->close();

		exit;
	}


	function Export_ODS(&$questions, $filename) {
		global $CFG;
		require_once("$CFG->libdir/odslib.class.php");

	/// Calculate file name
		$filename .= ".ods";
	/// Creating a workbook
		$workbook = new MoodleODSWorkbook("-");
	/// Sending HTTP headers
		$workbook->send($filename);
	/// Creating the first worksheet
		$sheettitle = get_string('reportanalysis','quiz_analysis');
		$myxls =& $workbook->add_worksheet($sheettitle);
	/// format types
		$format =& $workbook->add_format();
		$format->set_bold(0);
		$formatbc =& $workbook->add_format();
		$formatbc->set_bold(1);
		$formatb =& $workbook->add_format();
		$formatb->set_bold(1);
		$formaty =& $workbook->add_format();
		$formaty->set_bg_color('yellow');
		$formatyc =& $workbook->add_format();
		$formatyc->set_bg_color('yellow'); //bold text on yellow bg
		$formatyc->set_bold(1);
		$formatyc->set_align('center');
		$formatc =& $workbook->add_format();
		$formatc->set_align('center');
		$formatbc->set_align('center');
		$formatbpct =& $workbook->add_format();
		$formatbpct->set_bold(1);
		$formatbpct->set_num_format('0.0%');
		$formatbrt =& $workbook->add_format();
		$formatbrt->set_bold(1);
		$formatbrt->set_align('right');
		$formatred =& $workbook->add_format();
		$formatred->set_bold(1);
		$formatred->set_color('red');
		$formatred->set_align('center');
		$formatblue =& $workbook->add_format();
		$formatblue->set_bold(1);
		$formatblue->set_color('blue');
		$formatblue->set_align('center');
	/// Here starts workshhet headers
		$myxls->write_string(0,0,$sheettitle,$formatb);

		$headers = array(get_string('qidtitle','quiz_analysis'), get_string('qtypetitle','quiz_analysis'),
						get_string('qnametitle','quiz_analysis'), get_string('qtexttitle','quiz_analysis'),
						get_string('responsestitle','quiz_analysis'), get_string('rfractiontitle','quiz_analysis'),
						get_string('rcounttitle','quiz_analysis'), get_string('rpercenttitle','quiz_analysis'),
						get_string('qcounttitle','quiz_analysis'),
						get_string('facilitytitle','quiz_analysis'), get_string('stddevtitle','quiz_analysis'),
						get_string('dicsindextitle','quiz_analysis'), get_string('disccoefftitle','quiz_analysis'));

		foreach ($headers as $key => $header) {
			$headers[$key] = preg_replace('/<br[^>]*>/', ' ', $header);
		}

		$col = 0;
		foreach ($headers as $item) {
			$myxls->write(2,$col,$item,$formatbc);
			$col++;
		}

		$row = 3;
		foreach($questions as $q) {
			$rows = $this->print_row_stats_data($q);
			foreach($rows as $rowdata){
				$col = 0;
				foreach($rowdata as $item){
					$myxls->write($row,$col,$item,$format);
					$col++;
				}
				$row++;
			}
		}
	/// Close the workbook
		$workbook->close();

		exit;
	}

	function Export_CSV(&$questions, $filename) {

		$headers = array(get_string('qidtitle','quiz_analysis'), get_string('qtypetitle','quiz_analysis'),
						get_string('qnametitle','quiz_analysis'), get_string('qtexttitle','quiz_analysis'),
						get_string('responsestitle','quiz_analysis'), get_string('rfractiontitle','quiz_analysis'),
						get_string('rcounttitle','quiz_analysis'), get_string('rpercenttitle','quiz_analysis'),
						get_string('qcounttitle','quiz_analysis'),
						get_string('facilitytitle','quiz_analysis'), get_string('stddevtitle','quiz_analysis'),
						get_string('dicsindextitle','quiz_analysis'), get_string('disccoefftitle','quiz_analysis'));

		foreach ($headers as $key => $header) {
			$headers[$key] = preg_replace('/<br[^>]*>/', ' ', $header);
		}

		$text = implode("\t", $headers)." \n";

		$filename .= ".txt";

		header("Content-Type: application/download\n");
		header("Content-Disposition: attachment; filename=\"$filename\"");
		header("Expires: 0");
		header("Cache-Control: must-revalidate,post-check=0,pre-check=0");
		header("Pragma: public");

		echo $text;

		foreach($questions as $q) {
			$rows = $this->print_row_stats_data($q);
			foreach($rows as $row){
				$text = implode("\t", $row);
				echo $text." \n";
			}
		}
		exit;
	}

	function print_row_stats_data(&$q) {
		$qid = $q['id'];
		$question = get_record('question', 'id', $qid);

		$options = new stdClass;
		$options->para = false;
		$options->noclean = true;
		$options->newlines = false;

		$qtype = $question->qtype;

		$qname = format_text($question->name, FORMAT_MOODLE, $options);
		$qtext = format_text($question->questiontext, FORMAT_MOODLE, $options);

		$responses = array();
		foreach ($q['responses'] as $aid=>$resp){
			$response = new stdClass;
			if ($q['credits'][$aid] <= 0) {
				$qclass = 'uncorrect';
			} elseif ($q['credits'][$aid] == 1) {
				$qclass = 'correct';
			} else {
				$qclass = 'partialcorrect';
			}
			$response->credit = " (".format_float($q['credits'][$aid],2).") ";
			$response->text = format_text("$resp", FORMAT_MOODLE, $options);
			$count = $q['rcounts'][$aid].'/'.$q['count'];
			$response->rcount = $count;
			$response->rpercent =  '('.format_float($q['rcounts'][$aid]/$q['count']*100,0).'%)';
			$responses[] = $response;
		}
		$count = format_float($q['count'],0);
		$facility = format_float($q['facility']*100,0);
		$qsd = format_float($q['qsd'],4);
		$di = format_float($q['disc_index'],3);
		$dc = format_float($q['disc_coeff'],3);

		$result = array();
		$response = array_shift($responses);
		$result[] = array($qid, $qtype, $qname, $qtext, $response->text, $response->credit, $response->rcount, $response->rpercent, $count, $facility, $qsd, $di, $dc);
		foreach($responses as $response){
			$result[] = array('', '', '', '', $response->text, $response->credit, $response->rcount, $response->rpercent, '', '', '', '', '');
		}
		return $result;
	}
}

define('QUIZ_ALLATTEMPTS', 0);
define('QUIZ_HIGHESTATTEMPT', 1);
define('QUIZ_FIRSTATTEMPT', 2);
define('QUIZ_LASTATTEMPT', 3);

function stats_sumx($data, $initsum){
	$accum = $initsum;
	foreach ($data as $v) {
		$accum[0] += $v[0];
		$accum[1] += $v[1];
	}
	return $accum;
}

function stats_sumx2($data, $initsum){
	$accum = $initsum;
	foreach ($data as $v) {
		$accum[0] += $v[0]*$v[0];
		$accum[1] += $v[1]*$v[1];
	}
	return $accum;
}

function stats_sumxy($data, $initsum){
	$accum = $initsum;
	foreach ($data as $v) {
		$accum[0] += $v[0]*$v[1];
		$accum[1] += $v[1]*$v[0];
	}
	return $accum;
}

?>
